All of the surviving (37 of 39) episodes are now available on YouTube. Enter "Captain Midnight Decoder" into the YouTube search field, and it will take you to the three playlists: one is Captain Midnight only, one is Jet Jackson only, and the other is all 37 episodes, in order, necessarily mixing the 24 original (CM) with the syndicated 13 (JJ). Great stuff from 9/54 to 1/56.
UPDATE: the playlists have been streamlined into one, and marked more clearly.

…and you can swim the English channel, fight saboteurs in Mexico, and hit four home runs in the World Series. This is a simple, fun adventure show even though a little of Ichabod "Icky" Mudd goes a long way.

This is one of the earliest TV shows I can remember, and that memory consists of Sid Melton's character, the rocket plane, and the secret code given at the end of shows. I was 3 or 4 years old. My older sister had the decoder ring. We'd excitedly figure out the message. I hated Ovaltine.
As to Noah 8-?'s comment about I. Mudd, there were 2 episodes of Star Trek featuring the colorful character Harry (Harcourt Fenton) Mudd. One episode was called I, Mudd.
On watching this episode, I'd say this kids show was just as well made as any other adventure show I watched in those wee years, including Adventures of Superman, Lassie, Sky King, or The Lone Ranger.
I downloaded the 165MB MPEG4 file. Video was of low quality, showing compression artifacts, but tolerable. The audio quality was fine.

Great show! I knew of the radio show but not the TV show. But the TV.show was good to. An a person like me who loves TV history, this one will go down in my top ten. And it shows me that I still have a lot to learn about TV History.

Season 2, episode 2.
Origina;l air date: 5 October 1955.
Mr. Hobson, an Americam security specialist, reports that an enemy radio transmitter in Mexico has broken down. Since his men have broken the enemy`s code, they want the transmitter repaired as soon as possble So they can continue to monitor the broadcasts. Captsin Midnight and Icky volunteer to travel to the remote mountain area where the transmitter is located posing as fix-it men in hopes of being hired in repair the broken equipment - and do some pokig around in the enemy`s base on the side.
Cast: Richard Webb (Captain Midnight), Sid Melton (Ichabod `Ikky` Mudd), Olan Soule (Aristote `Tut` Jones, John Truax (Henry D, Davis), Tyler McVey (Hobson), Alan Wells (Nicko), Ben Frommer (Bandito), Edward Colmans (Commandante) and Alfred Ward (alvarez).
From IMDB,

Okaaaaaaayyyy..... Captain Midnight Opening then mention of 'Secret Squadron' and imbedded commercial... and What-the-Hey ... Isn't that Jet Jackson? and the "Secret" runway (how is something as big as an airfield with domed control center - hidden?)..... and the Music ! ! ! An' there's IGGY!!!!... being introduced as Ichabod Mudd? ? huh? What gives?
A visit to the IMDB website reveals these trivia gems:
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The first program to include audience participation through the use of the famous "Secret Decoder Ring" which allowed the afterschool TV viewer to decode Jet Jackson's secret orders.
--Wrong - Dead Wrong - maybe the first TELEVISION series but Ovaltine's Little Orphan Annie program did the same thing some 15 years earlier. Regarde' - same sponsor.
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Captain Midnight's plane was the Douglas "Skyrocket," a dual-powered experimental aircraft having both a jet engine and a four-barrel rocket engine.
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and now the good part - - -
1st) Captain Midnight was called 'Jet Jackson' in Australia, because Captain Midnight was the name of an infamous bushranger (outlaw).
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2th) The series' title was changed to "Jet Jackson, Flying Commando" because the program went into syndication after its initial two-year run but the ex-sponsor (Ovaltine) still owned the rights to the "Captain Midnight" title. Soundtrack references to "Captain Midnight" were overdubbed.
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Sooooooooooo..... I weren't rong ! ! it WAS Jet Jackson AKA Captain Midnight (Whoever ! )from my yout-hood's (middle to late 50's) Saturday Morning Tv fare.
After reading this post a coworker recognized something eles germane to this show. - Ichabod Mudd was the name of Jet Jackson's/Captain Midnight's sidekick..... maybe 15 years later Star Trek had a subordinate character called (now get this) I. Mudd. I'll just betcha that the name I.Mudd came from Iggy's full moniker.
Even though we are so much more scientifically sophisticated nowadays - I still give it 4 stars for its wildly imaginative psuedo-science.
Now if we can just get hold of Fury AKA Brave Stallion AKA possibly something else........
Noah 8-?